Choi decided to fight the discharge order.
"It's an immoral policy," he said, "It forces our soldiers to lie, it forces them into the closet, and the closet is not something that we need to force on our soldiers that have a hard enough time as it is."
Choi and his lawyer presented evidence to a military administrative board during a closed hearing in Syracuse, New York on Tuesday. Syracuse is the headquarters of the 27th Brigade Combat Team, which oversees Choi's National Guard unit.
The board is expected to make a recommendation to the commanding general of the first U.S. Army as to whether or not the discharge should stand.
The Associated Press contributed to this report.